[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 262033
TCDAT3
TROPICAL STORM LISA DISCUSSION NUMBER  30
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT SUN SEP 26 2004

THE CENTER OF LISA IS PARTIALLY EXPOSED AS THE CONVECTION REMAINS
PRIMARILY IN THE NORTHEAST QUADRANT AND WESTERLY SHEAR IMPACTS THE
SYSTEM. VISIBLE IMAGERY SUGGESTS THAT THE CENTER IS ELONGATED IN
THE NORTH-SOUTH DIRECTION. THE INITIAL INTENSITY HAS BEEN DECREASED
TO 45 KTS BASED ON TAFB AND SAB ESTIMATES THAT INDICATE A SLIGHT
DOWNWARD INTENSITY TREND. IN ADDITION...THE CLOUD TOP TEMPERATURES
IN THE PRIMARY CONVECTION HAVE ALSO DESCREASED SO THE INITIAL IS
SET TO 45 KTS.

INITIAL MOTION IS ESTIMATED TO BE 355/7. THE SHORT TERM MOTION HAS
BEEN NEARLY DUE NORTH...HOWEVER THE MODEL GUIDANCE DEPICTS THE
MOVEMENT OF LISA WILL BE PRIMARILY TO THE NORTH-NORTHWEST. LISA IS
CURRENTLY POSITIONED ON THE SOUTHEAST SIDE OF A MID-LEVEL HIGH
PRESSURE SYSTEM. LATER IN THE FORECAST PERIOD...LISA IS STEERED
ABOUT BY AN UPPER LOW LOCATED WEST OF THE SYSTEM. FOR THIS
ADVISORY...THE FORECAST GUIDANCE IS IN GOOD AGREEMENT ALTHOUGH THE
GFS IS GENERALLY LEFT OF TRACK EARLY IN THE FORECAST PERIOD AND
REJOINS THE GUIDANCE GROUP AT 72 HRS...AFTER WHICH THE VORTEX
TRACKERS LOSE THE CIRCULATION. THE FORECAST TRACK IS JUST TWEAKED A
BIT TOWARD CONU AND THE GUNS CONSENSUS WITH THE GREATEST ADJUSTMENT
OCCURRING AT 120 HRS.

THE INTENSITY FORECAST MODELS DO NOT STRENGTHEN LISA ABOVE TROPICAL
STORM STRENGTH UNTIL AFTER 72 HRS.  BY THIS TIME THE VERTICAL SHEAR
DECREASES TO LOW VALUES...SO THE WINDOW FOR ANY SIGNIFICANT
DEVELOPMENT IN LISA WOULD OCCUR LATER IN THE FORECAST PERIOD. THERE
IS LITTLE CHANGE IN THE NHC INTENSITY FORECAST.  NO SIGNIFICANT
CHANGE IS EXPECTED FROM 0-72 HRS...BUT LISA MAY REACH HURRICANE
STRENGTH IN THE EXTENDED TIME PERIOD...IF IT CAN SURVIVE THE
CURRENT SHEAR.

FORECASTER SISKO/PASCH

FORECAST POSITIONS AND MAX WINDS

INITIAL      26/2100Z 19.7N  46.1W    45 KT
 12HR VT     27/0600Z 20.9N  46.6W    45 KT
 24HR VT     27/1800Z 22.5N  47.5W    45 KT
 36HR VT     28/0600Z 23.8N  48.4W    50 KT
 48HR VT     28/1800Z 25.2N  48.9W    55 KT
 72HR VT     29/1800Z 28.1N  50.0W    65 KT
 96HR VT     30/1800Z 30.5N  51.0W    65 KT
120HR VT     01/1800Z 32.5N  52.0W    65 KT


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